The biochemical characterization of collagen structure and metabolism has reached a point where the basic methodology may be applied to specific disease entities. Diffuse pulmonary fibrosis occurs as an idiopathic entity or may be induced and is characterized by an overabundance of connective tissue. There has been little work on the collagen composition of normal lung. It is proposed to study pulmonary collagen metabolism from normal and fibrotic lungs both in vivo and in vitro. Using the techniques of salt and acid extraction, amino acid analysis, acrylamide disc gel electrophoresis, DEAE and CM-cellulose chromatography, and cyanogen bromide cleavage and mapping, collagen from normal and fibrotic lungs will be characterized, and the collagen produced by pulmonary fibroblasts in vitro from these tissues will be characterized. Biosynthetic rates of collagen production from normal and fibrotic pulmonary fibroblasts will be determined in vitro using tracer techniques. An attempt will be made to determine whether certain agents known to produce pulmonary fibrosis in vivo will do the same in vitro.